Your Green Roof Maintenance Strategy

Depending on the state of your green roof, you may want to carry out some level of maintenance.
Green roof maintenance

During very wet seasons green roofs can have problems retaining the nutrients that your plants need to remain healthy.  If the flowers have been in short supply then it may be time to apply a low nitrogen fertilizer.

If there are an abundance of flowers, this may be that the plants are heading for exhaustion and may need a ‘pick-me-up’ ready for the winter.

If you have sedum on your green roof, then too much rain or cold conditions can cause the sedum to change colours. Red indicates a sign of the plants going dormant.  This is typically seen during the winter months. If this is the case, your sedum roof could be fed with an organic fertilizer in the spring.

Basic Green Roof Maintenance: The 7 Point Plan

Depending on the state of your green roof, you may want to carry out the following procedures during maintenance:

  1. Removal of unwanted plant material, ie grasses, debris, etc.
  2. Correction of any localised plant encroachment ie. sedum in gutters.
  3. Replacement of any naturally failed plants and address any bare patches.
  4. Application of nutrient source.
  5. Removal of dead flower heads (if required). 
  6. Inspection of rainwater outlet chambers and surrounding vegetation breaks.
  7. Replenishment of any areas of settled substrate

General Green Roof Maintenance

General maintenance will normally be carried out annually during springtime. However, certain tasks such as the removal of weeds or accumulated leaf litter will be done during the Autumn.

All debris and leaves will be removed from the roof surface, rainwater outlets, chutes, gutters,

All debris from the roof will be removed to avoid suffocation of the sedum plants

Plant Encroachment

Any planting, which has encroached into drainage outlets, walkways and the vegetation barriers (pebbles), should be removed. This removed vegetation will be used to repair any bare patches if required. If movement/settlement of the pebble vegetation barrier has occurred, then additional washed stone pebbles (similar to the existing) will need to be added.

Weeding

Sedum blankets will at times include moss and grass. If considered excessive, provision should be made to remove any unwanted vegetation, e.g. weeds/ grasses/ saplings.  These can be removed manually by hand, or by using a ‘spot weed wipe’.  Weeds are a problem of aesthetics rather than damaging the roof, but large areas of weed or grass should be removed, as should saplings. After removal of weeds treat area as if it were a bare patch (see below).

Bare Patches

Bare patches should be repaired only during the growing season (March/April or late August until the end of September). Take clumps of Sedum from areas of abundant growth and place on bare patches pressing gently into the soil. They can then have a light sprinkling of sand mixed with compost.  The Sedum cuttings will grow best if this is carried out during spring maintenance and kept moist and free of temperature extremes (frost and intense sun).

Fertiliser

An annual application of a low nitrogen fertiliser should be applied for the sedum plants to remain healthy. Fertiliser to be applied during March/April.  This helps to prepare the plants for extreme weather conditions and flowering and also because it allows the different species to gain all their nutrients without competing against each other.  A good organic fertiliser should be applied at the rate of 80gm/m² using a hand held spreader or strewn by hand from a bucket.

Avoid fertiliser pellets settling on damp leaves as this may have a detrimental effect i.e. burning the leaves. The fertiliser should be lightly ‘watered in’ immediately after application.

Dung based organic fertilisers are to be avoided.

What Next?

To chat about your green roof maintenance issue or forthcoming project call us on 0844 057 0359. We’re happy to give advice and can supply everything you’ll need for your green roof including a root resistant membrane, your sedum and importantly your lightweight, organic green roof growing medium.